title: Inactivation of the SecA2 protein export pathway in Listeria monocytogenes promotes cell aggregation, impacts biofilm architecture and induces biofilm formation in environmental condition.
abstract: Listeria monocytogenes has a dichotomous lifestyle, existing as an ubiquitous saprophytic species and as an opportunistic intracellular pathogen. Besides its capacity to grow in a wide range of environmental and stressful conditions, L. monocytogenes has the ability to adhere to and colonize surfaces. Morphotype variation to elongated cells forming rough colonies has been reported for different clinical and environmental isolates, including biofilms. This cell differentiation is mainly attributed to the reduced secretion of two SecA2-dependent cell-wall hydrolases, CwhA and MurA. SecA2 is a non-essential SecA paralogue forming an alternative translocase with the primary Sec translocon. Following investigation at temperatures relevant to its ecological niches, i.e. infection (37°C) and environmental (20°C) conditions, inactivation of this SecA2-only protein export pathway led, despite reduced adhesion, to the formation of filamentous biofilm with aerial structures. Compared to the wild type strain, inactivation of the SecA2 pathway promoted extensive cell aggregation and sedimentation. At ambient temperature, this effect was combined with the abrogation of cell motility resulting in elongated sedimented cells, which got knotted and entangled together in the course of filamentous-biofilm development. Such a cell differentiation provides a decisive advantage for listerial surface colonization under environmental condition. As further discussed, this morphotypic conversion has strong implication on listerial physiology and is also of potential significance for asymptomatic human/animal carriage.
authors.affiliation: INRA, UR454 Microbiologie, Saint-Genès-Champanelle, F-63122, France.
authors.forename: Sandra
authors.initials: S
authors.lastname: Renier
authors.forename: Caroline
authors.initials: C
authors.lastname: Chagnot
authors.forename: Julien
authors.initials: J
authors.lastname: Deschamps
authors.forename: Nelly
authors.initials: N
authors.lastname: Caccia
authors.forename: Julie
authors.initials: J
authors.lastname: Szlavik
authors.forename: Susan A
authors.initials: SA
authors.lastname: Joyce
authors.forename: Magdalena
authors.initials: M
authors.lastname: Popowska
authors.forename: Colin
authors.initials: C
authors.lastname: Hill
authors.forename: Susanne
authors.initials: S
authors.lastname: Knøchel
authors.forename: Romain
authors.initials: R
authors.lastname: Briandet
authors.forename: Michel
authors.initials: M
authors.lastname: Hébraud
authors.forename: Mickaël
authors.initials: M
authors.lastname: Desvaux
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D002449:Cell Aggregation; D008089:Listeria monocytogenes / Q000166:cytology / Q000502:physiology*; D018613:Microscopy, Confocal; D013696:Temperature
chemical_list: D001426:Bacterial Proteins